By Anthony F. Gettins, David P. Stokes, Giles A. Taylor," and (in part) Christopher B. Judge, Department N-(Fluoren-9-ylidene)alkylamine N-oxides ( I ) react with diphenylketen to give spiro-oxazolidinones ( 2 ) and spiro-azetidinones (1 3). The adduct (2d) dissociates thermally to give the ylide ( 9 ) . The N-oxides (1) behave like normal nitrones in cycloaddition reactions with dipolarophiles.
S3 7HFDimethylketen reacts with N-(2.6-xylyl) benzylideneamine N-oxide to form a 7-oxabicyclo[4,3.0] nona-2.4-dien-8-one (V) resulting from a sigmatropic migration of an enolate anion.
of Sheffield Dimethylketen reacts with CN-diphenylnitrone to form the 1 : 1and 2 : 1 -adducts 2-(2-benzylideneiminophenyl) -2-rnethylpropanoic acid (IXa) and a(3,3-dimethyl-2-oxoindol-l -yl) benzyl isobutyrate (Illa), respectively. Similar adducts are formed from C-phenyl-N-(o-tolyl) nitrone.THE reactions of ketens with nitrones have been inthis work the reaction of dirnethylketen with CNvestigated by Staudinger.2 Several CN-diarylnitrones diphenylnitrone was examined in the hope that this were reported to form 1 : l-adducts with diphenylketen, might be a useful model system. It was immediately and a 1 : 2-adduct (nitrone to keten) was obtained from obvious, however, that the nitrone reacted in a totally triphenylnitrone. The structures proposed for these compounds all contained pentacovalent nitrogen and need not be considered further. of the structure of the 1 : l-adduct of diphenylnitrone PhCH = N \ & different manner. It reacted with an excess of dimethylketen in ethyl acetate solution to give a high yield of a 1 : 2-adduct, C,,H,,NO,.We assign the structure 3 T.
PREVIOUS studies on the reaction of dimethylketen with heteroaromatic N-oxides have shown that phenanthridine and isoquinoline N-oxides form adducts containing oxazepinedione rings and also undergo deoxygenation. We now report the results of an investigation of the reaction between pyridine N-oxide and dimethylketen.Dimethylketen failed to react with pyridine N-oxide in ethyl acetate, but reaction in benzene solution gave a mixture of products. Pyridine and 4-isopropylpyridine were isolated and characterised as their picrates, and acetone was isolated and identified as its dinitrophenylhydrazone. In addition, a very low yield of a crystalline solid, C,,H,,N04, was isolated having a composition corresponding to the combination of one molecule of pyridine N-oxide and two molecules of dimethylketen with one extra atom of oxygen.
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